Techniques for detecting micro-arcing occurring inside a semiconductor processing chamber

ABSTRACT

Some embodiments relate to a system. The system includes a radio frequency (RF) generator configured to output a RF signal. A transmission line is coupled to the RF generator. A plasma chamber is coupled to RF generator via the transmission line, wherein the plasma chamber is configured to generate a plasma based on the RF signal. A micro-arc detecting element is configured to determine whether a micro-arc has occurred in the plasma chamber based on the RF signal.

REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation U.S. application Ser. No. 16/232,404,filed on Dec. 26, 2018, which is a Continuation of U.S. application Ser.No. 15/855,128, filed on Dec. 27, 2017 (now U.S. Pat. No. 10,170,287,issued on Jan. 1, 2019), which claims the benefit of U.S. ProvisionalApplication No. 62/572,838, filed on Oct. 16, 2017. The contents of theabove-referenced Patent Applications are hereby incorporated byreference in their entirety.

BACKGROUND

Semiconductor production equipment, such as a plasma-enhanced chemicalvapor deposition (PE-CVD) systems, plasma etching systems, andsputtering systems, are used extensively throughout the production ofmodern day electronic devices. This semiconductor production equipmentmay contain a processing chamber lined with a dielectric material thatcontains a plasma inside the processing chamber. Due to the plasmahaving a higher electrical potential than the sidewalls of theprocessing chamber, breakdown of the dielectric material may occurcausing a micro-arc inside the processing chamber. In some cases, themicro-arcing causes contaminants from the processing chamber sidewall tocollect on a wafer being processed in the processing chamber resultingin a defective wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of some embodiments of a system fordetecting micro-arcing occurring inside a plasma chamber.

FIG. 2 illustrates some embodiments of a magnetic field generated by acurrent passing through a transmission line consistent with FIG. 1.

FIG. 3 illustrates some embodiments of a transmission line or plate.

FIG. 4 illustrates some embodiments of a transmission line or plate.

FIG. 5 illustrates some embodiments of a micro-arc detecting element,including a closed path conductive loop and micro-arcing detectioncircuitry.

FIG. 6 shows a timing diagram and chart that illustrate a magnetic-fieldsignal measured by a micro-arc detecting element as micro-arcing eventsoccur inside the plasma chamber.

FIG. 7 illustrates a method of some embodiments of detectingmicro-arcing occurring inside a plasma chamber.

DETAILED DESCRIPTION

The present disclosure will now be described with reference to thedrawings wherein like reference numerals are used to refer to likeelements throughout, and wherein the illustrated structures are notnecessarily drawn to scale. It will be appreciated that this detaileddescription and the corresponding figures do not limit the scope of thepresent disclosure in any way, and that the detailed description andfigures merely provide a few examples to illustrate some ways in whichthe inventive concepts can manifest themselves.

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Integrated circuit (IC) technologies are constantly being improved. Suchimprovements frequently involve scaling down device geometries toachieve lower fabrication costs, higher device integration density,higher speeds, and better performance. Due to device scaling, thenegative effects of micro-arcing (i.e., contaminants from the processingchamber collecting on a wafer) occurring in a plasma chamber arecompounded. For example, a plasma may be generated in a plasma chamberhaving a dielectric layer on the inner sidewalls of the plasma chamber.Due to the high electric potential of the plasma and low electricpotential of the sidewalls of the chamber, dielectric breakdown of thedielectric layer may occur inside the plasma chamber. When dielectricbreakdown occurs in the plasma chamber, current can flow through thedielectric layer causing a micro-arc to occur in the plasma chamber.This micro-arc may cause atoms from the inner sidewall, or thedielectric layer, to be ejected from the inner sidewall. These ejectedatoms will accumulate as contaminants on a wafer being processed insidethe processing chamber. Depending on the severity of the micro-arcing,the accumulation of contaminants will result in a faulty wafer requiringall or part of the wafer to be scrapped.

The present disclosure relates to a system for detecting micro-arcingoccurring inside a processing chamber. In some embodiments, the systemhas a radio frequency (RF) generator that outputs a RF signal. The RFgenerator is coupled to a matching network, and the matching network iscoupled to a plasma chamber via a transmission line. A magnetic-fielddetector is disposed proximate the transmission line and is configuredto measure a magnetic-field, which is generated due to RF current of theRF signal passing through the transmission line. By measuring themagnetic field of the RF signal along the transmission line, themagnetic-field detector can generate a magnetic-field signal withoutbeing in direct physical contact with the transmission line. Further, byproviding the magnetic-field signal in real-time and in-line with the RFsignal, micro-arcing occurring in the plasma chamber may be detected inreal-time and remedied. This can reduce the number of scrapped wafersand/or allow defective wafers to be identified early in the process tosave further unnecessary processing on the defective wafers.

FIG. 1 illustrates a block diagram of some embodiments of a system 100for detecting micro-arcing occurring inside a plasma chamber 106. Duringoperation of the plasma chamber 106, a vacuum pump 101 pumps an interiorcavity within the plasma chamber 106 down to vacuum, and the gas flowassembly 103 provides small amounts of gases used to form a plasma inthe plasma chamber 106. A controller 105 then triggers a radio frequency(RF) generator 102 to output an RF signal to ignite a plasma within theplasma chamber 106. In some embodiments, the RF generator 102 outputsthe RF signal as an analog RF signal to a matching network 104 andtransmission line 107. The RF generator 102 may be coupled to thematching network 104, which is configured to match a source impedance ofthe RF generator 102 to a load impedance of the plasma chamber 106. Insome embodiments, the source impedance is an impedance of the RFgenerator 102, and the load impedance is an impedance of the plasmachamber 106. Further, in some embodiments, the matching network 104matches the source impedance to about 50 ohms.

The plasma chamber 106 is coupled to the matching network 104 viatransmission line 107. The plasma chamber 106 may be, for example, aplasma-enhanced chemical vapor deposition chamber. Further, the plasmachamber 106 may have a dielectric layer disposed on the sidewalls of theplasma chamber 106, which separates an inner chamber of the plasmachamber 106 from an outermost housing of the plasma chamber 106. Thetransmission line 107 is configured to transmit a matched RF signal tothe plasma chamber 106 along a first plane (see first plane 202 in FIG.2). In some embodiments, the transmission line 107 is a metal plate, butthe transmission line 107 can also take the form of a coaxial cable,conductive micro-strip line, or twisted pair of copper wires, amongothers. The current of the RF signal transmitted via the transmissionline 107 generates a magnetic field around the transmission line 107.The magnetic field around the transmission line 107 flows in concentriccircles or ellipsoids in a second plane that perpendicularly intersectsthe first plane (see second plane 204 in FIG. 2).

FIG. 2 illustrates some embodiments of the first plane and the secondplane of FIG. 1. As illustrated, the magnetic field lines due to the RFsignal curve in concentric circles, ellipsoids, or other geometriesaround the transmission line 107 through the first plane 202 along asecond plane 204. Each point on a circle or ellipsoid has a magneticfield magnitude that is equal to that of other points on that circle orellipsoid, with different circles or ellipsoids representing differentmagnetic field magnitudes. In general circles or ellipsoids further fromthe transmission line 107 have smaller magnitudes than circles orellipsoids closer to the transmission line 107. Further, the magneticfield lines curve in a counterclockwise direction around thetransmission line 107 with respect to the conventional current flowdirection i. In other embodiments, the magnetic fields can have othergeometries, which depend on the shape of the transmission line 107 aswell as other magnets and/or currents near the transmission line 107 andthe magnetic-field sensor 112.

Referring back to FIG. 1, a micro-arc detecting element 110 isconfigured to determine whether a micro-arc has occurred in the plasmachamber 106 based on a magnetic-field signal. The magnetic-field signalhas a value in time that is proportional to the current provided to thetransmission line 107 in time.

In some embodiments, the micro-arc detecting element 110 comprises amagnetic-field sensor 112 and micro-arcing analysis circuitry 114.

The magnetic-field sensor 112 is disposed proximate the transmissionline 107. In some embodiments, the magnetic-field sensor 112 iscompletely outside the plasma chamber 106 and is disposed between afirst end of the transmission line 107 and a second end of thetransmission line 107. The magnetic-field sensor 112 may comprise a coilmade of a conductive material, such as copper, nickel, aluminum, orother metals or alloys. In some embodiments, the coil is a closedconductive path. The magnetic-field sensor 112 is configured to generatea magnetic-field signal, for example in the form of a current orvoltage, wherein the magnitude of the magnetic-field signal isproportional to the magnetic flux passing through the closed loop pathof magnetic-field sensor 112. Thus, the magnitude of the magnetic-fieldsignal is proportional to the magnetic field generated by the current(i_(RF)) of the RF signal along the transmission line 107. Themagnetic-field sensor 112 is disposed in such a way as to have themagnetic field, which is generated by the RF signal to flow in acounterclockwise direction around the transmission line 107, passthrough the coil and/or closed conductive path.

After the magnetic-field sensor 112 generates the magnetic-field signalbased on the RF signal passing through the transmission line 107, forexample in accordance with Ampere's law, the micro-arcing analysiscircuitry 114 is configured to evaluate the magnetic-field signal todetermine whether a micro-arc has occurred inside the plasma chamber106. If a micro-arc is detected, the wafer can be removed and evaluatedfor defects, and the plasma chamber 106 can be immediately shut downuntil it can be tested and/or repaired.

FIG. 3 shows an example where the transmission line 107 manifests as ametal plate which has a central trunk 302 and bulbous or circular ends304A, 304B on opposite ends of the central trunk 302. In someembodiments, the central trunk 302 is a rectangular-shaped plate thatextends symmetrically about either side of an axis 306, and the bulbousor circular ends 304A, 304B are equal in size with one another and areeach wider than the central trunk 302, and are arranged on oppositesides of the central trunk 302. In some embodiments, each bulbous orcircular end 304A or 304B is also symmetrical about either side of theaxis 306, so the axis 306 bi-sects the central trunk 302 and each of thebulbous or circular ends 304A, 304B.

In other embodiments, such as shown in FIG. 4, the transmission line 107manifests as a metal plate that has a rectangular “step-like” geometry.In FIG. 4, the rectangular plate has a central portion 402 that lies ona first plane, and first and second end portions 404, 406 that lie alongsecond and third planes, each of which is parallel to and spaced apartfrom the first plane. A first connecting portion 408 couples the centralportion 402 to the first end portion 404. The first connecting portion408 is perpendicular to the central portion 402 and the first endportion 404. A second connecting portion 410 couples the central portion402 to the second end portion 406. The second connecting portion 410 isperpendicular to the central portion 402 and the second end portion 406,and is in parallel with but spaced apart from the first connectingportion 408.

FIG. 5 shows some embodiments of the micro-arcing analysis circuitry114. The micro-arcing analysis circuitry 114 comprises a samplingelement 116, such as an analog to digital converter (ADC), coupled tothe closed path conductive loop 112. The sampling element 116 isconfigured to sample the magnetic-field signal 502 according to asampling clock 506, which is established by a sampling clock generator115, to generate a plurality of magnetic-field samples 504 that changein time. Further, the micro-arcing analysis circuitry 114 may comprisemicro-arcing detection logic 118 configured to evaluate whether at leastone magnetic-field sample of the plurality of magnetic-field samples 504has a magnitude that is greater than a transient magnetic-field maximumthreshold 508 or less than a transient magnetic-field minimum threshold510 to determine whether a micro-arc has occurred.

For example, in some embodiments, the RF signal has a frequency of 13.56MHz, and the sampling clock generator 115 has a sampling frequency of150 MHz. The sampling element 116 thus samples the magnetic-field signal502 and can store a 14-bit sample for each pulse of the sampling clock,with the digital value of the 14-bit sample corresponding to a magnitudeof the magnetic-field signal 502 at the sampled time. Further, themicro-arcing detection logic 118 can sample 150,000 sample values permillisecond, and compare those samples to obtain a maximum value amongthose 150,000 sample values. In cases when a “spike” or “drop” occurs inthe magnetic-field signal 502, which can correspond to a micro-arcevent, the digital value of the sample taken at the time of the “spike”or “drop” indicates the presences of the micro-arcing event. Forexample, in some cases, the micro-arcing event may be evidenced by a“spike” where the magnetic-field signal has a sudden maximum magnitudethat is between 3-4 times a steady-state maximum of the magnetic-fieldsignal 502, or may be evidenced by “drop” where the magnetic-fieldsignal has a sudden maximum magnitude that drops to less than half ofthe steady-state maximum of the magnetic-field signal 502. The durationof such a “spike” or “drop” may be relatively short, for example rangingfrom 1 microsecond to 100 microseconds, or may be relatively long, forexample ranging from 1 millisecond to several milliseconds.

In some embodiments, the micro-arcing analysis circuitry 114 maymanifest as an application specific circuit (ASIC) with transistors,semiconductor memory, and/or other semiconductor devices disposed on asemiconductor substrate and electrically coupled to one another toachieve desired functionality. In other embodiments, the micro-arcinganalysis circuitry 114 may manifest as a field programmable gate array(FPGA) that has been programmed to achieve desired functionality. Instill other embodiments, the micro-arcing analysis circuitry 114 canmanifest as a micro-processor coupled to semiconductor memory, withsoftware modules executing on the micro-processor to carry out desiredfunctionality. Thus, the micro-arcing analysis circuitry 114 may consistof dedicated hardware in some implementations, and in otherimplementations may correspond to a combination of hardware and softwareto achieve desired functionality.

FIG. 6 illustrates some embodiments of how the micro-arcing analysiscircuitry 114 and magnetic-field sensor 112 detect micro-arcing eventsinside the plasma chamber 106. For purposes of illustration, eight times602, 604, 606, 608, 610, 612, 614, 616 are illustrated and described inthe processing chamber. The uppermost portion of FIG. 6 depicts theplasma chamber 106 during each time period. As shown, for purposes ofillustration, during some of the time periods (e.g., 604, 608, 612, and616) a micro-arcing event is occurring in the plasma chamber 106, whileduring other time periods (e.g., 602, 606, 610, 614) a steady-stateplasma is contained in the plasma chamber 106 without micro-arcingoccurring.

In FIG. 6, the uppermost waveform is an example of the RF signal 108provided by the RF generator 102 to the plasma chamber 106 via thetransmission line 107. The RF signal 108 is in the form of atime-varying current, i_(RF). As illustrated, during time 602, the RFsignal 108 has a magnitude that oscillates according to a substantiallyconstant frequency while varying between a substantially constantsteady-state maximum amplitude (crest) 618 and substantially constantsteady-state minimum amplitude 620 (trough). Thus, in some embodiments,such as the illustrated embodiment of FIG. 6, the RF signal 108 is asimple sinusoidal waveform (e.g., sine or cosine wave pattern) having awavelength, λ, which corresponds to a single period of the waveform. Inthis example, each period of the waveform has two zero crossings and hasa single maximum (crest) and a single minimum (trough). However, inother embodiments, the RF signal 108 can manifest as a more complicatedsinusoidal waveform with higher harmonics. For example, the RF signal108 can be a square waveform, triangular waveform, saw-tooth waveform,or a more complicated waveform. Further, in other embodiments, the RFsignal 108 can have multiple relative minimums and multiple relativemaximums within each period of the waveform. In some embodiments, theperiod of the waveform can be approximately 74 ns, corresponding to afrequency of 13.56 megahertz (MHz), however in other embodiments theperiod of the wave can range from approximately 10 MHz to approximately30 MHz. In some cases, the waveform of the RF signal 108 can exhibit asubstantially steady-state condition in the absence of a micro-arcingevent, meaning that the waveform repeats with a substantially steadyfrequency, wavelength, and waveform shape at a regularly occurringperiod. In some embodiments, “substantially” in this context means thatthe frequency, wavelength, steady-state maximum amplitude andsteady-state minimum amplitude vary by no more than 10% during asteady-state plasma condition in the absence of micro-arcing.

The current of the RF signal, i_(RF), generates a magnetic field whosefield lines form circles or ellipsoids around the transmission line 107,such as previously illustrated in FIG. 2 for example. FIG. 6 shows someembodiments of the magnetic-field signal 502 as provided by the closedconductive path 112. The magnetic-field signal 502 is a time-varyinganalog signal whose voltage amplitude varies in time depending on theamount of magnetic flux passing through the closed conductive path ofthe magnetic-field sensor 112. Samples 504 of the magnetic-field signal(e.g., 512 a, 512 b), which are proportional to the RF signal, are thenmeasured according to a rising edge and/or falling edge of the sampleclock 506. Typically, one sample of the analog magnetic-field signal 502is taken at each pulse of the clock, with each sample 504 in FIG. 6being represented as an “x” (see e.g., 512 a, 512 b, 512 c, 512 d, 512e) that is superimposed on the magnetic-field signal 502. Thus, whilethe magnetic-field signal 502 is an analog signal, which variescontinuously in time, the magnetic field samples 504 (including 512 a,512 b, 512 c, 512 d, 512 e) are digital discrete values that areselected according to clock signal 506 and correspond to respectiveinstantaneous values of the magnetic-field signal 502.

The sampling frequency provided by the sampling clock 506 is greaterthan the frequency of the RF signal 108. For example, in someembodiments, the RF signal 108 has a frequency of 13.56 MHz, and thesampling frequency is 150 MHz. Thus, for each period or “pulse” of theRF signal 108, there are a little more than 11 magnetic field samplesthat are measured and stored. In other embodiments, the samplingfrequency can differ from 150 MHz, however, the sampling frequencyshould remain at least 3-4 times higher than the frequency of the RFsignal 108, and preferably 10 or more times higher than the frequency ofthe RF signal, to help ensure the sampling accurately characterizesbrief voltage excursions in the magnetic-field signal 502.

In some embodiments, each magnetic field sample 504 can be a multi-bitdigital value that is encoded to represent a magnitude of themagnetic-field signal 502 taken at the sampling time. For example, ifeach magnetic field sample is a 14-bit sample, each magnetic fieldsample is capable of representing 16384 different values. If the codingof these bits are chosen so that each code represents an incrementalvoltage change of 0.000125 volts (V), the 16384 different encodingvalues allow for each code to represent a unique voltage in a voltagerange of 2 V. Thus, if this voltage range is chosen to be arranged oneither side of 0 V, the 14 bits of any given sample can represent avoltage between positive −1 V and negative −1 V. For example, if anencoding value of b′00000000000000 could correspond to −1V, while anencoding value of b′111111111111 could correspond to +1 V. Of course,other encoding schemes could be used, and this example is in no waylimiting.

The micro-arc detecting element 110 determines an average steady-statemaximum amplitude value 624 of the magnetic-field signal 502 during thesteady-state of the RF signal when micro-arcs are not present. In someembodiments, for example, if the RF generator 102 is designed to drivethe plasma chamber 106 via the transmission line 107 by supplying a13.56 MHz signal whose voltage amplitude varies between +0.3 V and −0.3V, the average steady-state maximum amplitude 624 can be predeterminedto be +0.3 V. In other embodiments, the micro-arc detecting element 110analyzes the shape of the RF signal 108 by looking at the actualmagnetic field samples that have been measured, and selects actualmagnetic field samples that have the maximum amplitudes within somepredetermined time. For example, within time 602, the micro-arcdetecting element 110 can identify the magnetic field samplescorresponding to crests of the magnetic-field signal 504 (e.g., magneticfield samples 512 c, 512 d, and 512 e), and then optionally includesadditional magnetic field samples that are within a predeterminedexpected range of the magnetic field samples of the crests (e.g., rangebetween 624 l and 624 h). This allows the average steady-state maximumamplitude value 624 to account for slowly shifting or other dynamicconditions in the system.

The micro-arc detecting element 110 also determines an averagesteady-state minimum amplitude value 626 of the magnetic-field signal502 during the steady-state of the RF signal 108, which reflects thestate of the system when micro-arcs are not present. In someembodiments, for example, if the RF generator 102 is designed to drivethe plasma chamber 106 via the transmission line 107 by supplying the RFsignal 108 at 13.56 MHz, the average steady state minimum amplitude 626for the magnetic-field signal can be predetermined to be −0.3 V basedsolely on how the magnetic-field signal is expected to behave, and notbased on actual measurements or samples of the magnetic-field signal. Inother embodiments, the average steady state minimum amplitude 626 can bemeasured and/or can be predetermined without any measurements beingtaken, and in some embodiments can include samples within apredetermined expected range of the magnetic field samples of thetroughs (e.g., range between 626 l and 626 h).

During a first time 602, a wafer 650 is disposed within the plasmachamber 106, and a plasma is generated inside the plasma chamber 106without any micro-arcing occurring. Thus, the RF signal 108 during thistime is a steady-state sinusoidal signal, and correspondingly, themagnetic-field signal 502 has an average steady-state maximum 624 and anaverage steady-state minimum 626 which remain substantially constantover first time 602.

The magnetic-field signal 502 during the first time 602 oscillatesbetween the average steady-state maximum 624 and the averagesteady-state minimum 626. Thus, the magnetic-field signal indicates thatno micro-arcing event is occurring in the plasma chamber 106 duringfirst time 602. In some other embodiments, the magnetic-field signal 502(and corresponding magnetic field samples (e.g., 512 a, 512 b)) havepeaks and troughs that vary slightly from, but which are still within apredetermined expected range of average steady-state maximum 624 andaverage steady-state minimum 626 during 620. For example, the crestsduring first time 602 can have amplitudes that range from 90% of averagesteady-state maximum 624 and 110% of average steady-state maximum 624,which provides for some small variations in time for the characteristicsof the plasma within the plasma chamber. The troughs during first time602 can have amplitudes that range from 90% of average steady-stateminimum 626 and 110% of average steady-state minimum 626, which providesfor some small variations in time for the characteristics of the plasmawithin the plasma chamber.

A second time 604, which is referred to as a “spike” event, depicts theplasma chamber 106 with the plasma generated inside the plasma chamber106 and a micro-arcing event occurring. This micro-arcing event maydischarge material from the sidewall of the plasma chamber 106 and/orotherwise contaminate and/or damage the wafer 650. The magnetic-fieldsignal 502 during the second time 604 has a maximum amplitude 654 thatis at least three to four times the average steady-state maximum 624,and has a minimum amplitude 656 that is at least 3-4 times the averagesteady-state minimum 626. Thus, the magnetic-field signal 502 (andmagnetic field samples 512 a-512 e) are greater than a transient maximumthreshold 508 and/or less than a transient minimum threshold 510, andmay cross the transient magnetic-field maximum 508 and/or transientmagnetic-field minimum 510 multiple times in successive pulses of thewaveform. In some embodiments, a single instance of the magnetic-fieldsignal 502 (and magnetic field samples) crossing the transientmagnetic-field maximum threshold 508 or the lower transientmagnetic-field minimum threshold 510 indicates a micro-arcing event hasoccurred. In other embodiments, when the magnetic-field signal (andmagnetic field samples) crosses the transient magnetic-field maximumthreshold 508 or the transient magnetic-field minimum threshold 510 apredefined number of instances, the micro-arc detecting element 110indicates a micro-arcing event has occurred.

A third time 606 depicts the plasma chamber 106 with the plasmagenerated inside the plasma chamber 106 after a micro-arcing event hasoccurred, and the plasma chamber 106 has returned to steady-state. Afterthe micro-arc event has occurred, the magnetic-field signal remainssubstantially between the transient magnetic-field maximum threshold 508and the transient magnetic-field minimum threshold 510.

A fourth time 608 depicts the plasma chamber 106 with the plasmagenerated inside the plasma chamber 106 during another micro-arcingevent. In fourth time 608, the micro-arcing event is characterized by adrop in the maximum and minimums of the magnetic-field signal 502 (andmagnetic field sample values). In some embodiments, the presence of amicro-arcing event can be detected when the maximum amplitude for one ormore pulses of the waveform is reduced to 50% or less of the averagesteady-state maximum 624, and/or is reduced to 50% or less of theaverage steady-state minimum 626. In fourth time 608, the illustrated“drop” type micro-arcing event is illustrated as having a duration equalto the fourth time 608 and as reducing the frequency of the RF signal108 by approximately a factor of five, but in other embodiments, themicro-arcing event can have a longer duration (e.g., on the order ofmilliseconds) or a shorter duration (on the order of micro seconds) andthe RF signal and magnetic-field signal can retain the steady-statefrequency with diminished amplitude.

A fifth time 610 depicts the plasma chamber 106 after the plasma chamber106 has returned to steady-state. During fifth time 610, themagnetic-field signal remains substantially between the averagesteady-state maximum 624 and the average steady-state minimum 626.

During sixth time 612, the plasma is generated inside the plasma chamber106 during another micro-arcing event. In sixth time 612, themagnetic-field signal crosses the transient magnetic-field maximumthreshold 508 and the transient magnetic-field minimum threshold 510 fora longer period of time than depicted in the second time 604, butretains the same frequency as in second time 604.

A seventh time 614 depicts the plasma chamber 106 after the plasmachamber 106 has returned to steady-state. During seventh time 614, themagnetic-field signal remains substantially between the averagesteady-state maximum 624 and the average steady-state minimum 626.

An eighth time 616 depicts the plasma chamber 106 with the plasmagenerated inside the plasma chamber 106 after a micro-arcing event hasoccurred. As illustrated, the magnetic-field signal has a lowerfrequency at a lower amplitude than the other events. Thus, rather thanexhibiting a maximum amplitude that is 3-4 times the steady-statemaximum amplitude (as occurred during times 604 and 612), during eighthtime 616 the presence of micro-arcing event may be detected when themagnetic-field signal has a maximum value that is 2-3 times the averagesteady-state maximum 624 but with a frequency that is approximatelyone-third to one-fifth of the steady-state frequency.

It will be appreciated that the methodologies disclosed herein candetect micro-arcing conditions according to any of the times 604, 608,612, 616 depicted in FIG. 6, as well as variations on these events. Inmany cases, if micro-arcing is detected during the processing of anywafer, the system will immediate flag an error and stop processing forfuture wafers to limit overall contamination/defects on wafers withinthe fab.

FIG. 7 illustrates a method of some embodiments of detectingmicro-arcing occurring inside a plasma chamber. Although the steps ofthe method shown in FIG. 7 are described with reference to systemstructures which have been previously illustrated and described, it willbe appreciated that the method shown in FIG. 7 is not limited to thepreviously illustrated and described structures but rather may standalone separate of the method. Further still, the order of the acts orsteps depicted is not limiting, and the acts or steps can be carried outin other orders with additional acts or steps being added or withillustrated acts or steps being omitted, depending on theimplementation.

At 702, one or more wafers are loaded into a plasma chamber. In someembodiments, a wafer can be a monocrystalline semiconductor wafer madeentirely of monocrystalline silicon, while in other embodiments thewafer can be an semiconductor-on-insulator (SOI) substrate, whichincludes a handle substrate, an insulating layer disposed over thehandle substrate, and a semiconductor layer (e.g., epitaxially grownsilicon layer) disposed over the insulating layer. In many instances,the wafer can take the form of a disc-like (e.g., circular) wafer. Sucha wafer can have a diameter of 1-inch (25 mm); 2-inch (51 mm); 3-inch(76 mm); 4-inch (100 mm); 5-inch (130 mm) or 125 mm (4.9 inch); 150 mm(5.9 inch, usually referred to as “6 inch”); 200 mm (7.9 inch, usuallyreferred to as “8 inch”); 300 mm (11.8 inch, usually referred to as “12inch”); or 450 mm (17.7 inch, usually referred to as “18 inch”); forexample. Other substrates which are not wafers, but rather can take theform of rectangular chips, and/or other shapes, can also be processed.

At 704, an RF signal is provided to a matching network, such as matchingnetwork 104 in FIG. 1 to generate a matched RF signal.

At 706, the matched RF signal is provided to a transmission line, suchas transmission line 107 in FIG. 1.

At 708, a plasma is generated inside a plasma chamber, such as plasmachamber 106 illustrated in FIG. 1, by receiving the matched RF signalfrom the transmission line.

At 710, a magnetic-field signal is generated by measuring a magneticfield generated by the matched RF signal.

At 712, the magnetic-field signal is sampled to provide magnetic-fieldsignal sample values. A sampling frequency at which the magnetic-fieldsignal is sampled is greater than an RF frequency of the RF signal.

At 714, micro-arcing occurring in the plasma chamber is detected bycomparing the magnetic-field signal sample values to a pre-definedmagnetic-field pattern.

At 716, a determination is made whether a micro-arc has been detectedwithin the plasma chamber while the one or more wafers are beingprocessed. If not (‘NO’ at 716) then the detection procedurecontinuously repeats, and the method returns to 704 until this group ofwafers is unloaded from the plasma chamber for processing. After thegroup of wafers is unloaded, the next group of wafers can be loaded intothe plasma chamber and the method can repeat for the next group ofwafers.

On the other hand, however, if a micro-arc was detected (‘YES’ at 716)at any time during which the one or more wafers are being processed, themethod proceeds to 718 and takes action to reduce an extent of damagestemming from the micro-arc that occurred in the plasma chamber. Forexample, the wafer(s) present in the chamber when the micro-arc occurredcan be removed from the chamber and subjected to a battery of additionaltests to determine whether any contaminations or defects are present dueto the micro-arc. For example, the wafers can be evaluated usingmicroscopy techniques in which the wafer is visually inspected todetermine the presence of contamination or defects on the surface of thewafer; or can be evaluated using functional tests in which electricalbiases (e.g., test vectors) are applied to test pads of the chips on thewafer to check whether the chips on the wafer return the correctexpected results on test pads of the chips. In comparison, if amicro-arc is not detected while a group of wafers is being processed,that group of wafers can in some instances not be subjected to thebattery of additional tests, but can be moved directly to the nextprocessing apparatus.

Further still, taking action to reduce the extent of damage stemmingfrom the micro-arc detected in the plasma chamber can include shuttingdown the plasma chamber before any additional wafers are processed inthe plasma chamber. This immediate shut down is a particular advantageof this approach, because previous approaches have been unable to detectmicro-arcs within a plasma chamber in real time. Because of thisinability of previous systems, even if a wafer was damaged due to amicro-arc event, it was difficult to determine whether the cause of thecontamination was a micro-arc within a given plasma chamber. Therefore,to previously identify a micro-arcing issue, a large number of waferswhich suffered from contamination would only be identified further downthe manufacturing process, and significant investigation would occur toisolate the cause of the contamination to be the plasma chamber. Becauseof the time involved with previous investigation, a significant numberof wafers could be damaged before the faulty plasma generator, whichsuffered from micro-arcing, would be identified and shut down. With thepresent techniques, micro-arcing can be readily identified in real-time;and a technician can be dispatched to the tool to repair any issues tominimize the number of wafers that are contaminated due to themicro-arcing.

Thus, as can be appreciated from above, some embodiments relate to asystem. The system includes a radio frequency (RF) generator configuredto output a RF signal. A transmission line is coupled to the RFgenerator. A plasma chamber is coupled to RF generator via thetransmission line, wherein the plasma chamber is configured to generatea plasma based on the RF signal. A micro-arc detecting element isconfigured to determine whether a micro-arc has occurred in the plasmachamber based on the RF signal.

Other embodiments relate to a system including a radio frequency (RF)generator configured to output a radio frequency (RF) signal. Atransmission line is coupled to the RF generator, and a plasma chamberis coupled to the RF generator via the transmission line. The plasmachamber is configured to generate a plasma based on the RF signal. Amagnetic-field sensor includes a closed conductive path proximate to thetransmission line. The magnetic-field sensor is configured to generate amagnetic-field signal that varies in time commensurate with atime-varying magnetic flux passing through the closed conductive path. Amicro-arc detecting element is configured to determine whether amicro-arc has occurred in the chamber based on a magnitude of themagnetic-field signal.

Still other embodiments relate to a system for detecting micro-arcinginside a plasma chamber. The system includes a radio frequency (RF)generator configured to output an RF signal to a matching network. Atransmission line has a first end coupled to a matching network and asecond end coupled to a plasma chamber. The first end is configured toprovide the RF signal along a first plane to the second end that iscoupled to a plasma chamber. The RF signal generates a magnetic fieldaround the transmission line, and the magnetic field flows in concentriccircles or ellipsoids which reside on a second plane that isperpendicular to the first plane. A magnetic-field sensor includes acoil that extends laterally in a closed loop between the first end ofthe transmission line and the second end of the transmission line. Thecoil is offset from the transmission line. The magnetic field flowsthrough the closed loop. A micro-arc detecting element is configured toreceive a signal from the magnetic-field sensor and determine whether amicro-arc has occurred in the chamber based on the signal from themagnetic field sensor.

Other embodiments relate to a method for detecting micro-arcing inside aplasma chamber. In the method, an RF signal is provided to a matchingnetwork to generate a matched RF signal. The matched RF signal isprovided to a transmission line. A plasma is generated inside a plasmachamber by receiving the matched RF signal from the transmission line. Amagnetic-field signal is generated by measuring a magnetic fieldgenerated by the matched RF signal. The magnetic-field signal is sampledto provide magnetic-field signal sample values. Micro-arcing occurringin the plasma chamber is detected by determining whether themagnetic-field signal sample values correspond to a pre-definedmagnetic-field pattern.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A system to detect micro-arcing in a plasmawithin a plasma chamber, the system comprising: a magnetic-field sensorconfigured to generate a magnetic-field signal based on a magnetic fluxcorresponding to the plasma; and micro-arc detecting logic configured todetermine an average steady-state maximum amplitude for themagnetic-field signal over a first time in which the plasma is in asteady-state, and further configured to determine whether a first typeof micro-arcing is present in the plasma chamber by evaluating whether amagnitude of the magnetic-field signal over a second time is less thanthe average steady-state maximum amplitude by at least a first amount.2. The system of claim 1, wherein the magnetic-field sensor comprises aclosed conductive path, and wherein the magnetic-field sensor isconfigured to generate the magnetic-field signal that varies in timecommensurate with a time-varying magnetic flux passing through theclosed conductive path.
 3. The system of claim 1, wherein themagnetic-field sensor is configured to determine whether a magnitude ofthe magnetic-field signal over a third time exceeds the averagesteady-state maximum amplitude by at least a third amount to determinewhether a second type of micro-arcing is present in the plasma chamber.4. The system of claim 1, wherein the magnetic-field sensor isconfigured to determine whether a magnitude of the magnetic-field signalover a third time exceeds a predetermined integer multiple of theaverage steady-state maximum amplitude by at least a second amount todetermine whether a second type of micro-arcing is present in the plasmachamber, the predetermined integer multiple being greater than one. 5.The system of claim 1, further comprising: a radio frequency (RF)generator configured to output a RF signal; a transmission line coupledto the RF generator; and wherein the plasma chamber is coupled to the RFgenerator via the transmission line, wherein the plasma chamber isconfigured to generate the plasma based on the RF signal.
 6. The systemof claim 5, wherein the micro-arc detecting logic is configured tosample the magnetic-field signal at a sampling frequency, therebyproviding a plurality of magnetic-field samples, and further configuredto determine whether a micro-arc has occurred in the plasma chamberbased on the plurality of magnetic-field samples.
 7. The system of claim6, wherein the sampling frequency is greater than an RF frequency of theRF signal.
 8. A system to detect micro-arcing in a plasma within aplasma chamber, the system comprising: a magnetic-field sensorconfigured to generate a magnetic-field signal based on a magnetic fluxcorresponding to the plasma; and micro-arc detecting logic configuredto: determine whether a first type of micro-arcing is present in theplasma chamber during a first time based on whether a magnitude of themagnetic-field signal over the first time exceeds an averagesteady-state maximum amplitude of the magnetic-field signal by at leasta first amount, and determine whether a second type of micro-arcing ispresent in the plasma chamber during a second time based on whether amagnitude of the magnetic-field signal over a second time is less thanthe average steady-state maximum amplitude by at least a second amount.9. The system of claim 8, further comprising: a radio frequency (RF)generator configured to output a RF signal; a transmission line coupledto the RF generator; and wherein the plasma chamber is coupled to the RFgenerator via the transmission line, and wherein the plasma chamber isconfigured to generate the plasma based on the RF signal.
 10. The systemof claim 9, wherein the micro-arc detecting logic is configured tosample the magnetic-field signal at a sampling frequency, therebyproviding a plurality of magnetic-field samples, and is furtherconfigured to determine whether a micro-arc has occurred in the plasmachamber based on the plurality of magnetic-field samples.
 11. The systemof claim 10, wherein the sampling frequency is greater than an RFfrequency of the RF signal.
 12. The system of claim 8, wherein themagnetic-field sensor comprises a closed conductive path, wherein themagnetic-field sensor is configured to generate the magnetic-fieldsignal that varies in time commensurate with a time-varying magneticflux passing through the closed conductive path.
 13. The system of claim8, wherein the magnetic-field sensor is configured to determine whethera magnitude of the magnetic-field signal over the first time exceeds apredetermined integer multiple of the average steady-state maximumamplitude by at least a third amount to determine whether the first typeof micro-arcing is present in the plasma chamber, the predeterminedinteger multiple being greater than one.
 14. A system comprising: aradio frequency (RF) generator configured to output a RF signal; atransmission line coupled to the RF generator; a plasma chamber coupledto RF generator via the transmission line, wherein the plasma chamber isconfigured to generate a plasma based on the RF signal; a closed pathconductive loop proximate to the transmission line and configured togenerate a magnetic-field signal, the magnetic-field signal having anamplitude proportional to an amount of magnetic flux which passesthrough the closed path conductive loop and which arises due to the RFsignal passing through the transmission line; and a micro-arc detectingelement configured to sample the magnetic-field signal at a samplingfrequency, thereby providing a plurality of magnetic-field samples, andfurther configured to determine whether a micro-arc has occurred in theplasma chamber based on the plurality of magnetic-field samples.
 15. Thesystem of claim 14, wherein the sampling frequency is greater than an RFfrequency of the RF signal.
 16. The system of claim 14, wherein themicro-arc detecting element is configured to determine an averagesteady-state maximum amplitude for the magnetic-field signal over afirst time in which the plasma is in a steady-state, and furtherconfigured to determine whether a magnitude of the magnetic-field signalover a second time exceeds the average steady-state maximum amplitude byat least a first amount to determine whether a first type ofmicro-arcing is present in the plasma chamber.
 17. The system of claim14, wherein the micro-arc detecting element is configured to determinean average steady-state maximum amplitude for the magnetic-field signalover a first time in which the plasma is in a steady-state, and furtherconfigured to determine whether a magnitude of the magnetic-field signalover a second time exceeds a predetermined integer multiple of theaverage steady-state maximum amplitude to determine whether a first typeof micro-arcing is present in the plasma chamber, the predeterminedinteger multiple being greater than one.
 18. The system of claim 14,wherein the micro-arc detecting element is configured to determine anaverage steady-state maximum amplitude for the magnetic-field signalover a first time in which the plasma is in a steady-state, and isfurther configured to determine whether micro-arcing is present in theplasma chamber by evaluating whether a magnitude of the magnetic-fieldsignal over a second time is less than the average steady-state maximumamplitude.
 19. The system of claim 18, wherein the micro-arc detectingelement is further configured to determine whether a magnitude of themagnetic-field signal over a third time exceeds a predetermined integermultiple of the average steady-state maximum amplitude to determinewhether micro-arcing is present in the plasma chamber, the predeterminedinteger multiple being greater than one.
 20. The system of claim 18,wherein the micro-arc detecting element is further configured todetermine whether a magnitude of the magnetic-field signal over a thirdtime exceeds the average steady-state maximum amplitude by at least afirst amount to determine whether micro-arcing is present in the plasmachamber.